1. Field of the Invention
The present invention relates to a device for detachably securing a filtering sheet to an air bed using fine solid particles. In such an air bed, the sheet serves to prevent the particles from spreading out of the bed, while the air can pass through the filtering sheet.
2. Description of the Related Art
The air bed of the kind mentioned above has been known and is disclosed in Japanese Patent Publication No. 54-128,196 and Japanese Utility Model No. 58-108,832. The bed comprises a bed body, a large number of ceramic beads arranged in the bed body, a filtering sheet provided to cover an opening in the bed body, and means for supplying an air stream from a bottom plate of the bed body. The air stream serves to move or agitate the ceramic particles. Due to the movement of the particles and the air stream passing through the filtering sheet, a patient lying on the sheet is floated to some extent. Therefore, the pressure applied to the patient is made uniform, so that the pain of the patient can be mitigated to a large extent and a curing effect can be promoted. Due to the above-mentioned merits, air beds have been utilized in hospitals mainly for burnt patients and very sick patients. The filtering sheet of the air bed is made from strong synthetic fibers and is placed on the mass of the solid ceramic particles in a slightly loose manner, but the periphery of the filtering sheet is fixed to a flange of the bed in an airtight manner in order to prevent the particles from being blown out of the bed by the air stream.
Patients do not lay directly on the filtering sheet, but conventional bed sheets belonging to respective patients are placed on the filtering sheet to prevent the filtering sheet from becoming stained and soiled. Furthermore, an old filtering sheet will not perform the filtering function very well, so that such an old filtering sheet has to be replaced by a new one. Therefore, the filtering sheet is detachably secured to the air bed.
In Japanese Patent Publication No. 54-128,196, there is disclosed a device for detachably securing the filtering sheet to the air bed. However, this known device utilizes a joint having a special construction, so that the operation for either removing or securing the filtering sheet either from or to the air bed is rather cumbersome. Furthermore, it is difficult to attain the complete airtight coupling required between the filtering sheet and the air bed.